While useful for other purposes, the present invention was developed in view of a vexing energy loss problem in steam systems. Thus, while disclosed below, for convenience, in terms of energy loss detection in steam systems, it is not intended to limit the invention to that environment.
In conventional steam systems, steam is transferred as a source of heat energy to a load. As heat energy is transferred to the load, the steam condenses. A steam trap then discharges this condensate, while retaining the steam within the system. However, as the steam trap wears out, steam is increasingly lost from the trap and such losses can develop into a significant energy waste.
Three methods have commonly been used in an attempt to determine the steam loss of a steam trap and such known methods are listed below, along with disadvantages thereof.
1. The first prior known method is based on visual observation. This method requires the output, or discharge, of the trap to the atmosphere for observation. However, atmospheric discharge is not always possible, due to the way that the trap has been piped, or installed, into a condensate return system.
Moreover, with several different types of steam traps available on the market, visual observation requires considerable training and skill to determine steam losses. While it may be possible to determine with some reliability that a gross trap failure has occurred, estimating the magnitude of any steam losses cannot be done accurately as the following table illustrates
______________________________________ Trap at 150 psig At Atmospheric Discharge Changes Discharges Pressure Mass Flow to Volume Flow ______________________________________ 1. 82 #/hr. Cond. 68.6 #/hr. Cond. 1.15 cu.ft./hr. Cond. 0 #/hr. Steam 13.4 #/hr. Steam 360 cu.ft./hr. Steam 2. 50 #/hr. Cond. 41.6 #/hr. Cond. .695 cu.ft./hr. Cond. 5 #/hr. Steam 13.4 #/hr. Steam 360 cu.ft./hr. Steam ______________________________________
In the table above, Trap 1 has no steam loss, but actually discharges a considerable amount of steam at atmospheric pressure due to flashing of the condensate as the pressure is reduced. As the human eye actually sees a volume flow, in the above examples a large cloud of steam and a few drops of water would be seen.
On the other hand, Trap 2, which is defective and has a steam loss, discharges the same volume of steam as trap 1 but a somewhat smaller volume of condensate. However, the human eye would be very hard pressed to determine which of these two traps actually had a steam loss.
2. The second prior known method is based on a pyrometer. In some areas it has been common practice to test traps by reading upstream and downstream trap temperatures with a pyrometer. If the temperature difference is very high, the trap has been considered to be in satisfactory condition, while if the temperature difference is very low, the trap has been considered to be defective.
This tends to be a very dubious method as the outlet temperature follows the saturation temperature/pressure relation for steam. A trap with a high rate of steam loss, discharging to a much lower pressure, will display a very high temperature difference. On the other hand, a good trap, discharging through a very low pressure difference, will display very low temperature difference. In actual field service with a condensate return system, the trap outlet pressure is seldom, if ever, known. Accordingly, such temperature difference readings can be highly misleading as to the condition of the trap.
3. The third prior known method is based on sonic or ultrasonic monitoring. A highly trained person using a stethoscope or an ultrasonic device can inspect a trap for steam loss. However, considerable skill and training is required to understand the normal mode of operation of all the various available traps and to be able to distinguish abnormal operation. Sound devices generally can only be used to make a good/bad judgment of trap operation, and cannot accurately quantify the magnitude of a steam loss.
Accordingly, such known prior methods have not been entirely satisfactory for monitoring energy losses in a bi-phase fluid system, particularly for monitoring steam losses in a steam trap.
Accordingly, the objects of this invention include provision of:
An energy loss detecting apparatus which is free of the foregoing limitations of the above-discussed known prior methods.
A system, as aforesaid, which, for measuring a steam loss in a steam trap, remains at supply steam pressure and avoids pressure drops as may cause flashing of condensate to steam, and which is capable of high accuracy by measuring directly the steam loss to the steam trap.
A system, as aforesaid, capable of monitoring steam trap condition regardless of the type of steam trap operating in the steam circuit.
A system, as aforesaid, capable of displaying steam flow (or loss) in any desired units, and capable of reducing the skill level required of the operator in determining steam loss, as compared with steam loss detection methods above discussed.
A system, as aforesaid, capable of separating a mixture of vapor and liquid into separate streams and measuring the velocity of the vapor phase independent of the condition of the liquid phase.
A system, as aforesaid, capable of measuring energy loss in terms of the flow rate of the vapor phase of a bi-phase fluid, and wherein the flow rate measurement can readily be implemented, for example by a temperature responsive probe.
Other objects and purposes of this invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspection of the accompanying drawings.